Centralized detection with decentralized implementation in Java Encoder QR in Java Centralized detection with decentralized implementation bar code for .NET

Centralized detection with decentralized implementation use none none integrating togenerate none on barcode generator 128c The defense system d none for none escribed in Section 17.3 is fully distributed. However, the drawback of this system is that it may have a relatively high storage complexity.

Meanwhile, each node needs to have prior knowledge of the set of legitimate traf c pairs, which might not be available to all nodes in general. Next we describe a modi ed version of the defense system. In the modi ed version, instead of performing attacker detection by itself, each good node will report the observed information to certain nodes, which we call centralized detectors.

Then the centralized detectors will perform attacker detection on the basis of the traf c information collected. In general, the centralized detectors will be under stronger protection than those normal nodes and may have more powerful computational capability and more storage. The detailed description of the modi ed defense system is as follows.

First, the routediscovery and packet-delivery procedure is the same as that described in Section 17.3.1.

Second, the monitoring mechanism is still the header-watcher mechanism as described in Section 17.3.2.

To reduce the storage overhead, we made the following modi cation: for each good node, instead of storing all valid packet headers that have been read, most times it is not necessary to store any packet headers locally, but only to store the threetuple (traf c pair, sequence number, route) associated with each valid packet header that has been read. A good node needs to record a whole packet header only if it has been requested to do so by the detectors, as will be explained next. Furthermore, instead of reporting each item of packet-header information that has been read separately, each good node will report the packet-header information that has been read in a batch mode, that is, each report consists of many items of packet-header information.

Assuming that in the previous fully distributed mechanism a good node needs to store n number of packet headers with each having l bytes (l is usually more than 100 bytes for a route request with 10 relays, considering the extra signatures), then, in the modi ed defense. Microsoft Official Website Defense against traf c-injection attacks mechanism, it need s none none tore only n l bytes, where l is usually much smaller than l. For example, for a route with 10 relays, each node ID uses 8 bits, and the sequence number uses 32 bits, so l is only 14 bytes. Further, normal nodes do not need to know which source destination pairs are legitimate or their legitimate traf c-injection rates.

The centralized detectors perform the job of detecting traf c-injection attacks by applying detection rules similar to those described in Section 17.3.3.

The major difference lies in that, when the centralized detector performs detection, there are usually two steps involved. In the rst step, the detector will check whether a node has injected two packets with the same sequence number or whether a sequence number is larger than a speci ed upper bound solely on the basis of the partial packet-header information that has been collected, that is, without checking the packet-header signatures. If either of the two conditions has been satis ed, the detector will then request those nodes which report such information to submit full packet headers.

That is, the centralized detector needs solid evidence in order to mark a node as an attacker. Now we use an example to illustrate the modi ed detection procedure. Assume that node a has reported a sequence number seq1 and route R1 associated with traf c pair (s, d), and node b has reported a sequence number seq2 and route R2 associated with traf c pair (s, d).

After the centralized detector has received these reports, it will nd that seq1 = seq2 but R1 = R2 . Then the detector has reason to suspect that s has launched traf c-injection attacks. When this happens, the detector will ask nodes a and b to report the full packet headers next time, so that it can collect concrete evidence on the basis of which to charge s.

From the above description we can see that, although the detection is performed in a centralized manner, the monitoring is still fully distributed. Now we analyze the detection performance of the modi ed defense system. It is easy to see that either a simple IDPA or a long-route IDPA can easily be detected.

Meanwhile, for a multi-route IDPA, requiring packets sent via different routes to use different sequence numbers produces no gain from the attacker s point of view, and allowing packets sent via different routes to use the same sequence number will be detected immediately when an omnidirectional transmission technique is used. Now we focus on the scenario in which attackers that allow packets sent via different routes to use the same sequence number will be detected immediately, and hence a directional transmission technique is used to avoid their being detected. Given that an attacker s picks n node-disjoint routes to simultaneously inject packets and packets on different routes will share the same set of sequence numbers, as long as at least two nodes on the selected routes are good, it is easy to check that there is zero probability that s can avoid being detected.

In other words, attackers have no chance of launching an IPDA without being detected. That is to say, under the modi ed defense mechanism, the attackers success probability is much lower than that under the previous fully distributed defense mechanism, which is the major advantage of the modi ed mechanism. Compared with the fully distributed defense system described in Section 17.

3, the storage overhead of the modi ed defense system can be dramatically reduced, but some extra communication overhead is introduced due to the fact that each node needs to.
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